Originally published in Interiors & Sources

06/28/2013

Dodge HVAC Pitfalls in LEED-EBOM

How the ventilation prerequisite can present barriers without careful planning

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Is your building bringing in enough outside air to meet LEED-EBOM requirements? There are three ways to determine whether your HVAC system performs well enough.

Looking at LEED certification for your existing building?

Before you start evaluating what level you could achieve, make sure you’re giving due consideration to the mandatory prerequisites. Assuming that your building meets them all can come back to haunt you later in the process.

This is especially true for requirements like the Indoor Environmental Quality prerequisite (IEQp1) – you don’t want to find out near the end of your project that you need to run more ducting to tenant spaces because previous build-outs didn’t include this feature.

Preparing for hurdles to the IEQ prerequisite early in the process will help ensure you can navigate them easily.

1) Methods of Compliance
There are three ways to prove you meet the requirements of this prerequisite – natural ventilation, IAQ testing, and ventilation rate. You only need to satisfy one, and your choice will depend on the characteristics of your building and its existing HVAC system.

The natural ventilation requirement is only a truly viable option in certain climates and building types, explains Chris Ashworth, managing director of the eastern region for Healthy Buildings, a firm specializing in indoor air quality, energy, and water consulting to the commercial real estate industry.

Paragraph 5.1 of ASHRAE 62.1 covers how to confirm that your naturally ventilated building complies.

For buildings with mechanical ventilation, you’ll choose between the ventilation rate procedure and the indoor air quality (IAQ) procedure. The former relies on a standardized calculation that accounts for each space’s square footage and main function (office, lab, etc.), while the latter tests for specific pollutants.

“The calculation is very systematic, and that’s a benefit,” Ashworth says. “Once you know how much outdoor air to provide, you can measure it and confirm against that. It’s much less subjective because ASHRAE is telling you that for an office space, for instance, you need .06 cfm per square foot and 5 cfm per person.”

The IAQ procedure is best suited for buildings that have mechanical ventilation but can’t bring in enough outdoor air based on the ventilation rate procedure.

This compliance path is not explicitly permitted by LEED, but is currently in a pilot phase with the USGBC that could lead to its adoption as an alternate path, Ashworth explains.

If you qualify for this route, you’ll have to demonstrate that your current system is unable to provide the mandated flow rates.

“The ventilation rate procedure tells you that you’re bringing in a certain amount of outdoor air, whereas the IAQ procedure would say ‘Here are the contaminants that are in the space.’ It’s still something tangible,” Ashworth says. “It may actually give you more data on the building. It’s the same intent, but you’re testing the air for contaminants.”


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